To create a material with superior properties than the separate components.
1 of 28
What are reinforcements?
They increase thee stiffness and strength of matrix (glass,,ceramics,graphene)
2 of 28
Why is a 'matrix 'used'?
To allow the load to be transferred to the strong phase, separate the fibres and prevent cracks from passing through a section, to prevent surface abrasion in the case of brittle fibres.
3 of 28
What are the stages of processing a composite?
Reinforcemnt: Shape,compress . Introduce matrix -. fill regular between reinforcement with the matrix in liquid or glass form. Material: Vacuumed to reduce voids. Solidify
4 of 28
Decribe Polymer matrix hand lay up
The repeated application of layers.
5 of 28
What are the advantages and disadvantages of hand lay up
Adv: High quality components, low cost, no press, no autoclave. Disadv: Operator dependent, only addidtion polymerisation, voids are common
6 of 28
Describe spray up
Fibres cut to pre-determined length and deposited into mould together with resin. Produces large/complex components, random fibre orientation, smooth finish only on inner surface.
7 of 28
What are 'metal matrix composites'?
Continuous fibre reinforced metal composite.
8 of 28
Describe the coated- fibre method
Wind+plasma spray with metal, diffusion bond, infiltrate (creates uniform structure).
9 of 28
What does Tows - bundle of filaments do?
Disperse fibres,coat or infiltrate, treat like single monofilaments.
10 of 28
How are 'metal matrix composites' produced?
Through liquid metal infiltration, use a preform containing short fibres. Then infiltrate under pressure. Good metal flow is needed. MMC reinforced at points of stress.
11 of 28
What is stir- casting?
Creates high volume mmc products, pre-treatment needed to ensure wetting of particles.
12 of 28
Explain co-spraying of Metal matrix composites
Spray- casting of metal matrix and ceramic particles together. Product is only 90% dense. Fine microstructure may be produced.
13 of 28
What are Carbon-Carbon composites?
Carbon fibres in form of woven fibres
14 of 28
Describe vapour phase impregnation
Gas e.g. methane deposits carbon. (There is a problem of pore blocking which leads to high internal porosity which can be solved by low gas pressure or intermediate heat treatment)
15 of 28
What is liquid impregnation?
Phenolic resins used = low yield of carbon
16 of 28
How can oxidation be inhibited?
Coating matrix with inhibitors(use sealed coating). An outer layer of SiC can be used.
17 of 28
Give an expression for mass of the composite
W_c=W_r +W_m
18 of 28
Give an expression for volume of the composite
V_c =V_r +V_m
19 of 28
Give an expression for volume fraction of the composite
Φ_r =V_r/V_c ; Φ_m = V_m/V_c
20 of 28
Give an expression for density of the composite
ρ_c = W_c/V_c ; ρ_c =Φ_r *ρ_r +Φ_m *ρ_m
21 of 28
What is the relationship between density of the reinforcement and the matrix?
Reinforcements usually have a greater density than the matrix.
22 of 28
What is a packing geometry?
Shape that packing of fibres creates e.g square, hexagonal
23 of 28
Give an expression for the volume fraction of a fibre which is packed in an hexagonal array
Φ_f = π/2root(3) *(r/R)^2
24 of 28
Give an expression for the volume fraction of a fibre which is packed in an square array
Φ_f = π/4 *(r/R)^2
25 of 28
What happens when r=R?
Hexagonal:Φ_f =0.907; Square: Φ_f = 0.785
26 of 28
What is the fibre -foil method
Fibres are heated between matrix metal foils (creates a non-uniform structure)
27 of 28
What is PITCH?
PITCH gives high porosity - improves material and removes porosity by hot isotactic pressing in both liquid and vapour impregnation.
28 of 28
Other cards in this set
Card 2
Front
What are reinforcements?
Back
They increase thee stiffness and strength of matrix (glass,,ceramics,graphene)
Comments
No comments have yet been made